1. Field of the Invention
The present invention relates to a saddle type vehicle having mounted thereon a power unit which includes a twin clutch type transmission having main shafts and clutches along different axes.
2. Description of Background Art
Hitherto, there has been known a vehicle power unit provided with a twin clutch type transmission wherein gear trains for a plurality of gear speeds established selectively are provided between a pair of main shafts disposed in parallel to each other and a counter shaft having an axis parallel to the main shafts, and wherein the pair of main shafts are coaxially provided with respective clutches for permitting/interrupting the transmission of power from a crankshaft (see, for example, Japanese Patent Laid-Open No. 2008-303939). This configuration is advantageous over the case where a pair of clutches are coaxially overlappingly arranged, in that an increase in the width in the axial direction of the power unit can be suppressed.
Meanwhile, the vehicle power unit having a pair of main shafts and a pair of clutches on different axes as in the related art has a problem that since the space for layout of each of the shafts in it tends to be increased as compared with a power unit having main shafts and clutches in a coaxial fashion, it influences the vehicle body size when used as a power unit for a small-type vehicle (saddle type vehicle) such as a motorcycle.
In addition, in a saddle type vehicle such as a motorcycle, a swing arm is mounted rearwardly of a crankcase at a front portion thereof through a pivot shaft so as to be swingable upward and downward, and a rear wheel as a drive wheel is rotatably supported on a rear portion thereof. In this case, a power unit having two main shafts tends to have a long distance from the crankshaft to the pivot shaft, and, when one of the main shafts is disposed rather on the upper side and the other rather on the lower side so as to prevent the distance from increasing, the degree of freedom in laying out the peripheral parts is lowered.
Accordingly, it is an object of the present invention, in a saddle type vehicle having mounted thereon a power unit including a twin clutch type transmission having a pair of main shafts and a pair of clutches along different axes, to enable a compact layout of axes and to contrive reductions in size of the unit and its surroundings.